In a hydraulic excavator, a boom, an arm, and a bucket constituting a front work device are rotatably supported, and when the boom, the arm, or the bucket is moved singly, the bucket forward end draws an arcuate locus. Thus, in forming a linear finish surface with the bucket forward end through, for example, an arm drawing operation, it is necessary for the operator to perform a combined operation on the boom, the arm, and the bucket, and great skill is required of the operator.
In this regard, a technique is available according to which a function (machine control) by which the driving of the hydraulic actuators is controlled automatically or semi-automatically by a computer (controller) is applied to excavation work, with the bucket forward end being moved along the design surface (target excavation surface) at the time of excavation operation (at the time of operation of the arm or the bucket) (Patent Document 1).
On the other hand, some conventional hydraulic excavators are equipped with a hydraulic regeneration device which causes the hydraulic fluid in the tank side line of a hydraulic actuator to flow into the pump side line (hydraulic fluid regeneration), thereby increasing the operational speed of the hydraulic actuator (Patent Document 2).